Nickel base superalloys have been extensively studied for many years. As a result, numerous alloys have been developed which display desireable properties under adverse operating conditions. Because of their properties, nickel base superalloys have found wide application in gas turbine engines. The following United States patents disclose some nickel base alloy compositions which have been developed for use in the gas turbine engine industry. All compositions are on a weight percent basis.
U.S. Pat. No. 4,222,794 describes a single crystal nickel base superalloy having desireable high temperature mechanical properties and resistance to oxidation and hot corrosion. The composition of this alloy is 4.5-6.0 Cr, 0.0-7.0 Co, 1.7-2.3 Mo, 4.0-6.0 W, 1.0-5.0 Re, 5.0-5.8 Al, 0.8-1.5 Ti, 5.5-5.8 Ta, 0.2-0.6 V, with the balance nickel.
U.S. Pat. No. 4,371,404 describes a single crystal nickel base superalloy whose composition is 6.5-8.2 Cr, 3.0-8.0 Co, 1.7-2.3 Mo, 3.0-5.0 W, up to 3.0 Re, 4.5-5.5 Al, 0.7-1.5 Ti, 10.0-13.5 Ta, with the balance nickel.
Other U.S. Patents which are indicative of the general state of the art relative to single crystal nickel base superalloys are U.S. Pat. Nos. 4,116,723 and 4,402,772.
U.S. Patents which describe columnar grained nickel base superalloys are e.g., 3,526,499, 3,887,363, 3,904,402, 3,944,416, 4,169,742, 4,284,430, 4,292,076, 4,388,124, 4,522,664, and Re. 29,920. These superalloy compositions include grain boundary strengthening agents such as C, B, and Zr. Single crystal nickel base superalloys such as those of the present invention achieve their desireable mechanical properties in the absence of such grain boundary strengthening elements.